DESCRIPTION (adapted from the application) This application is submitted in response to RFA announcement DK-00-005, "Foodborne Illnesses, Gastrointestinal and Renal Complications." A new program for developing a strategy for determining the infectivity of Norwalk virus and other Norwalk-like viruses is proposed. Norwalk-like viruses are the single, most important cause of foodborne illness, but to date no system for determining the infectivity of these viruses exists. Two approaches will be pursued using the Norwalk virus strain to determine the infectivity of these viruses: (1) development of an in vitro method for virus cultivation in cell culture and (2) development of a biosensoring method to permit the rapid detection of potentially infectious Norwalk-like viruses. Several features make Norwalk virus, the prototype strain of NLVs, an attractive candidate to use in the development of in vitro measures of Norwalk-like virus infectivity: (i) virus stock for which infectivity in humans has been determined will be available; (ii) sensitive methods for detecting complete or partial Norwalk virus replication have been developed, including RT-PCR assay, immunofluorescence assays, and in situ-RT-PCR assays; (iii) fresh stool samples containing Norwalk virus (from human experimental infection studies) are expected to be available during the grant period; (iv) and hyperimmune animal and acute and convalescent human sera are available for use in neutralization assays. The assays developed initially using Norwalk virus will then be generalized to other Norwalk-like viruses. The results obtained from our studies will generate new knowledge about the replication of Norwalk-like viruses and develop systems for assessing determining correlates of immunity from infection and measuring virus viability after exposure to different environmental conditions.